1. Field of the Invention
The present invention relates, generally, to check rings and seals for injection molding machines and more particularly, but not exclusively, the invention relates to check rings and seals for metal injection molding machines and die casting machines.
2. Background Information
The state of the art includes U.S. Pat. No. 3,578,803 issued May 18, 1971 to Huhn that describes the use of a spiral spring to urge a seal ring towards a counter-ring to create a seal on a shaft.
U.S. Pat. No. 3,655,206 issued Apr. 11, 1972 to Durametallic Corp. describes the use of a spiral sealing ring that is pressed against a wedge shaped surface to apply a radially inward and axial compressive force to the sealing ring to form a seal around a shaft. The sealing ring is constructed of multiple layer graphite material. The sealing ring is designed to maintain a seal around the shaft.
U.S. Patent Application 2002/0100507 published Aug. 1, 2002 by Hauser et al describes a check valve for a piston pump in an automotive braking system. The check valve is formed as a single piece consisting of a helical coil with a base ring on one end and a closure disk on the other end. Movement of the base ring provides the opening and closing of the check valve. The helical spring provides the opening and closing mobility of the valve. The outer surfaces of the helical spring are not used as closing or sealing surfaces.
U.S. Patent Application 2004/0001900 published Jan. 1, 2004 by Dominka describes a check valve for an injection system. The valve includes a shut-off pin, a spring guide member and a helical spring. The helical spring is compressed by the guide member to force the pin to close the flow path and decompressed to enable the flow path to open. The surfaces of the helical spring are in contact with the flow path but do not provide any of the closing or sealing surfaces.
None of the prior art suggests the use of a spiral coil to actually seal a flow channel.
There is a need for a wear resistant reliable seal for sealing the flow path through check valves in injection molding machines.